IIO: add DT bindings for stm32 DFSDM filter

Add bindings that describes STM32 Digital Filter for Sigma Delta
Modulators. DFSDM allows to connect sigma delta
modulators.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt
new file mode 100644 (file)
index 0000000..911492d
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt
@@ -0,0 +1,128 @@
+STMicroelectronics STM32 DFSDM ADC device driver
+
+
+STM32 DFSDM ADC is a sigma delta analog-to-digital converter dedicated to
+interface external sigma delta modulators to STM32 micro controllers.
+It is mainly targeted for:
+- Sigma delta modulators (motor control, metering...)
+- PDM microphones (audio digital microphone)
+
+It features up to 8 serial digital interfaces (SPI or Manchester) and
+up to 4 filters on stm32h7.
+
+Each child node match with a filter instance.
+
+Contents of a STM32 DFSDM root node:
+------------------------------------
+Required properties:
+- compatible: Should be "st,stm32h7-dfsdm".
+- reg: Offset and length of the DFSDM block register set.
+- clocks: IP and serial interfaces clocking. Should be set according
+               to rcc clock ID and "clock-names".
+- clock-names: Input clock name "dfsdm" must be defined,
+               "audio" is optional. If defined CLKOUT is based on the audio
+               clock, else "dfsdm" is used.
+- #interrupt-cells = <1>;
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Optional properties:
+- spi-max-frequency: Requested only for SPI master mode.
+                 SPI clock OUT frequency (Hz). This clock must be set according
+                 to "clock" property. Frequency must be a multiple of the rcc
+                 clock frequency. If not, SPI CLKOUT frequency will not be
+                 accurate.
+
+Contents of a STM32 DFSDM child nodes:
+--------------------------------------
+
+Required properties:
+- compatible: Must be:
+       "st,stm32-dfsdm-adc" for sigma delta ADCs
+       "st,stm32-dfsdm-dmic" for audio digital microphone.
+- reg: Specifies the DFSDM filter instance used.
+- interrupts: IRQ lines connected to each DFSDM filter instance.
+- st,adc-channels:     List of single-ended channels muxed for this ADC.
+                       valid values:
+                               "st,stm32h7-dfsdm" compatibility: 0 to 7.
+- st,adc-channel-names:        List of single-ended channel names.
+- st,filter-order:  SinC filter order from 0 to 5.
+                       0: FastSinC
+                       [1-5]: order 1 to 5.
+                       For audio purpose it is recommended to use order 3 to 5.
+- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers".
+
+Required properties for "st,stm32-dfsdm-adc" compatibility:
+- io-channels: From common IIO binding. Used to pipe external sigma delta
+               modulator or internal ADC output to DFSDM channel.
+               This is not required for "st,stm32-dfsdm-pdm" compatibility as
+               PDM microphone is binded in Audio DT node.
+
+Required properties for "st,stm32-dfsdm-pdm" compatibility:
+- #sound-dai-cells: Must be set to 0.
+- dma: DMA controller phandle and DMA request line associated to the
+               filter instance (specified by the field "reg")
+- dma-names: Must be "rx"
+
+Optional properties:
+- st,adc-channel-types:        Single-ended channel input type.
+                       - "SPI_R": SPI with data on rising edge (default)
+                       - "SPI_F": SPI with data on falling edge
+                       - "MANCH_R": manchester codec, rising edge = logic 0
+                       - "MANCH_F": manchester codec, falling edge = logic 1
+- st,adc-channel-clk-src: Conversion clock source.
+                         - "CLKIN": external SPI clock (CLKIN x)
+                         - "CLKOUT": internal SPI clock (CLKOUT) (default)
+                         - "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
+                         - "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
+
+- st,adc-alt-channel: Must be defined if two sigma delta modulator are
+                         connected on same SPI input.
+                         If not set, channel n is connected to SPI input n.
+                         If set, channel n is connected to SPI input n + 1.
+
+- st,filter0-sync: Set to 1 to synchronize with DFSDM filter instance 0.
+                  Used for multi microphones synchronization.
+
+Example of a sigma delta adc connected on DFSDM SPI port 0
+and a pdm microphone connected on DFSDM SPI port 1:
+
+       ads1202: simple_sd_adc@0 {
+               compatible = "ads1202";
+               #io-channel-cells = <1>;
+       };
+
+       dfsdm: dfsdm@40017000 {
+               compatible = "st,stm32h7-dfsdm";
+               reg = <0x40017000 0x400>;
+               clocks = <&rcc DFSDM1_CK>;
+               clock-names = "dfsdm";
+               #interrupt-cells = <1>;
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               dfsdm_adc0: filter@0 {
+                       compatible = "st,stm32-dfsdm-adc";
+                       #io-channel-cells = <1>;
+                       reg = <0>;
+                       interrupts = <110>;
+                       st,adc-channels = <0>;
+                       st,adc-channel-names = "sd_adc0";
+                       st,adc-channel-types = "SPI_F";
+                       st,adc-channel-clk-src = "CLKOUT";
+                       io-channels = <&ads1202 0>;
+                       st,filter-order = <3>;
+               };
+               dfsdm_pdm1: filter@1 {
+                       compatible = "st,stm32-dfsdm-dmic";
+                       reg = <1>;
+                       interrupts = <111>;
+                       dmas = <&dmamux1 102 0x400 0x00>;
+                       dma-names = "rx";
+                       st,adc-channels = <1>;
+                       st,adc-channel-names = "dmic1";
+                       st,adc-channel-types = "SPI_R";
+                       st,adc-channel-clk-src = "CLKOUT";
+                       st,filter-order = <5>;
+               };
+       }